Removal section for well casing



Jan. 25, 1966 v. s. CLAY ETAL 3,231,019

REMOVAL SECTION FOR WELL CASING Filed Aug. 22, 1963 3 Sheets-Sheet 1 Hill 4a 3:. 4s a i 2* 4 i 44 5 5 I a FIG.1

INVENTORS VICTOR S. CLAY LESTER 1 K/NSMAN 1966 v. s. CLAY ETAL REMOVAL SECTION FOR WELL CASING 3 Sheets-Sheet 2 Filed Aug. 22, 1963 Jan. 25, 1966 v. s. CLAY ETAL 3,231,019

REMOVAL SECTION FOR WELL CASING Filed Aug. 22, 1963 3 Sheets-Sheet 3 q) 0 a I L :2 f )A f g E Q S2 33 g R K N f \\T\ n v E N &

INVENTORS VICTOR S. CLAY LESTER l. K/NSMAN United States Patent 3,231,019 REMOVAL SECTION FOR WELL CASING Victor S. Clay, Costa Mesa, and Lester V. Kinsman,

Fullerton, Calif., assignors to Chevron Research Company, a corporation of Delaware Filed Aug. 22, 1963, Ser. No. 303,747 11 Claims. (Cl. 16624) This invention relates to casing and completing wells and, more particularly, this invention relates to methods and apparatus for providing an open interval at a predeterminable location in the casing of an oil well.

Heretofore it has been the practice as one of the steps in many oil well completions to case a borehole with a string of connected pipe sections. The individual pipe sections are called well casing sections and the coupled sections are called a casing string. The casing string is formed and run into the well by successively lowering a first casing section into the well, connecting a second casing section to the first section, lowering the connected sections further into the well and connecting a third section to the second section and so forth. Casing sections are connected by means of mating threads in the ends of the sections. After a string of easing has been run into a well, cementing operations are performed to secure the casing string in the hole and to provide a water seal between the casing and the well wall. The cementing operation or cement squeeze is usually accomplished by forcing cement down the interior of the casing string, out the bottom of the string and up into the annular space between the exterior of the casing string and the well Wall. The cement is allowed to harden to securely seal the casing string in the well.

When it is desired to produce oil from a petroleumbearing formation penetrated by the well, the casing string must be opened at the producing zone so that oil can flow into the well. Heretofore one manner of accomplishing this was perforating the casing by suitable means such as a gun perforator. Using this technique small holes can be opened in the casing at the selected interval by firing bullets to penetrate the casing. In many producing formations however satisfactory production is not obtained through the small holes thus created. Therefore it is often desirable to completely remove a portion of the casing string to expose a large interval of the well wall. For example, it is not unusual to desire to expose an interval, commonly called a window, of 100 feet or more of the well wall while leaving the casing cemented in place both above and below the exposed section or window. Oftentimes it is desired to expose an interval of as much as 500 feet or more. Heretofore the window was opened by means of milling or cutting out the steel casing over the entire interval with a drilling tool to form the opening. Obviously, cutting away this much steel is an expensive and time-consuming operation.

Therefore it is a principal object of this invention to provide a removable tubular member which is connectable at a desired interval into the casing string to serve as part of the casing string during running-in operations and which is located in the well with the casing string during cementing operations but which member is easily removable after the cement has hardened without cutting or milling the steel casing over the entire interval of the well that it is desired to expose.

Briefly, the present invention provides for disconnectably connecting a tubular member into the casing string at a preselected interval. The tubular member has a smaller maximum outside diameter than the inside diameter of the casing sections. The tubular member is formed of a material and in a manner to function adequately as a portion of the casing string during runningin operations as the string is being run into the well.

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Sheath means adapted to prevent cement from contacting and hardening on the tubular member are formed around the tubular member.

In one form the sheath means comprises a protective sheath formed around the tubular member. The protective sheath is secured around the tubular member and the ends of the sheath are closed off to prevent cement from contacting the tubular member. The sheath means is formed of an easily removable material and has an outside diameter approximating the outside diameter of the casing. The tubular member and the protective sheath thereon are connected at a selected interval in the casing string and run into the well as a part of the casing string. Cementing operations are done after the casing string including the tubular member and the protective sheath means are in place in the well. The sheath means prevents cement from contacting and thus sticking to the tubular member. After the cement hardens or at some later time the tubular member is disconnected from the casing string and removed up the interior of the casing string. The sheath means and the cement adhering thereto are then easily removed as by abrading, milling, dissolving or other suitable means to expose a desired interval of the well wall.

Further objects and advantages of the present invention will be apparent from the following detailed description read in light of the accompanying drawings which are a part of this specification and in which:

FIGURE 1 is a sectional view and illustrates a preferred embodiment of apparatus assembled in accordance with the present invention;

FIGURE 2 is a sectional view and illustrates a preferred embodiment of apparatus assembled in accordance with the invention and connected in a casing string and cemented in a well therewith;

FIGURE 3 is a sectional view and illustrates a preerred embodiment of apparatus assembled in accordance with the invention being disconnected from the casing string;

FIGURE 4 is a section view and illustrates a preferred embodiment of apparatus assembled in accordance with the present invention and disconnected from the casing string being removed from the well;

FIGURE 5 is a sectional view taken at line 5-5 of FIGURE 2;

FIGURE 6 is a sectional view of an earth formation penetrated by a well and illustrates a casing string being run into the well;

FIGURE 7 is a sectional view of an earth formation penetrated by a well and illustrates the preferred embodiment of apparatus of the present invention connected with the lower portion of the casing string for running into a well therewith;

FIGURE 8 is a sectional view of an earth formation penetrated by a well and illustrates the preferred embodiment of apparatus of the present invention connected between the lower portion of the casing string and the beginning of an upper portion of the casing string for running into a well;

FIGURE 9 is a sectional view of an earth formation penetrated by a well and illustrates the preferred embodiment of apparatus of the present invention connected in the casing string for running into a well.

Before discussing the specific embodiments of the present invention, a general understanding and appreciation of the invention is best gained by referring to the drawings and, in particular, to FIGURES 24 which illustrate apparatus assembled in accordance with the invention cemented in a well with a casing string (FIGURE 2); the first step in removing the removable portion of the apparatus (FIGURE 3); and the removable portion of the apparatus being pulled from the Well leaving only the protective portion and the cement on the well wall (FIG- URE 4). The protective portion and the cement are then removable to expose a desired interval of well wall in the casing string.

Referring now to FIGURE 1, a preferred embodiment of apparatus assembled in accordance with the present invention is shown. The apparatus is illustrated disconnectably connected between casing sections 21 and 22. The casing sections 21 and 22 are preferably standard well casing sections having appropriate threaded connections at the pin end and the box end. As illustrated in FIG- URE 1 the apparatus of the present invention connects the box ends of casing sections 21 and 22; however, it is obvious that the arrangement of apparatus can be modified in accordance with the present invention to connect a box end to a pin end or a pin end to a pin end for example. Tubular member 24, which may be formed of a number of sections, such as sections 28 and 29, connected together to form a tubular member of the desired length, is connected with means, such as adapter collars 26 and 27 for connection between the casing sections 21 and 22. The tubular sections 28 and 29 making up the tubular member 24 are provided with mateable right-hand threads for connection together.

Lower adapter collar 27 has APT standard connecti-on right-hand threads 30 mateable with the standard connection right-hand threads 31 of easing section 22. Suitable threads are 7" diameter8 round threads. The adapter collar 27 thus can be attached to casing section 22 by a threaded connection. Low friction left-hand threads 32 are provided in the adapter collar 27. The low friction left-hand threads are mateable with low friction left-hand threads 33 located on the lower end of tubular member 24. The tubular member 24 is connectable to the casing section 22 by means of threads provided in the lower adapter collar 27. The upper adapter collar 26 has API right-hand standard connection male threads 34 mateable with corresponding threads 35 formed in the box end of casing section 21. The upper end of tubular member 24 has low friction left-hand threads 36 mateable with the low friction left-hand threads 37 formed in upper adapter collar 26. The upper portion of tubular member 24 is provided with threads 38. The threads 38 are right-hand threads. Thus the tubular member 24 is adapted to be connected between two sections of casing 21 and 22 and to function as a portion of the casing string during running-in operations. That is to say, the tubular member 24 is formed of a material such as steel for example, which has adequate strength to support the weight of the casing string as it is being hung in the well. The tubular member is also adapted to serve as a portion of the casing string to allow circulation of drilling fluids and other conventional operations performed with the casing string.

In accordance with the present invention a protective sheath 40 is formed around the exterior of the tubular member 24 to prevent cement from hardening on it and thus sticking the tubular member 24 in the well. The protective sheath 40 is preferably formed of a material which is easily removable from the well at some later time. A preferred material is plastic pipe. Other suitable materials include rubber pipe and paper pipe. Any material which will prevent cement from contacting the tubular member, which material is easily millable or otherwise removable at a desired later time and inside of which the tubular member is rotatable, is useful in accordance with the present invention.

As shown in FIGURE the protective sheath is formed around tubular member 24. An annular space 42 is provided between sheath 40 and tubular member 24. In many operations it is desired to fill the annular space 42 with a substance 43 to prevent collapse of the sheath 40. The substance 43 may also provide lubrication so that tubular member 24 is more easily rotatable inside sheath 40. In this regard a hole 44 is provided in the upper portion of sheath to allow entry of drilling fluid, grease or other suitable lubricating material. The hole is closable by suitable means after the annular space has been filled with the lubricating fluid 43. The lower end of sheath 4%) is securely held in place by means of an annularly extending sleeve 45 which is affixed to the lower adapter collar 27. The upper end of the sheath 4! is connected to the upper adapter collar 26 by suitable means such as annularly extending groove 46 and plastic cement.

With reference now to FIGURE 2, FIGURE 3, and FIGURE 4, the features and advantages of the apparatus of the present invention will be more fully described. As shown in FIGURE 2 the casing string which includes upper casing section 21, tubular member 24 and lower casing section 22 has been run into a well 50 which penetrates producing interval 86 to a desired location. The tubular member 24 is disconnectably connected in the casing string between casing sections 21 and 22 by suitable means such as heretofore described adapter collars 26 and 27. Cement, represented by numeral 51, has been forced into the annular space between the well 50 and the exterior of the casing string and all-owed to harden to securely cement the casing string in the well. Sheath 40 prevents the cement from contacting tubular member 24. Further, there is some space in the form of an annular chamber 42 provided between tubular member 24 and sheath 40. When it is desired to expose the producing interval of the well wall, generally represented by the numeral 80, a drill string 52 or other suitable means is run from the surface down the interior of the casing string. The end of the drill string is provided in a suitable manner with right-hand threads 53 mateab'le with the right-hand threads 38 in the interior of tubular member 24. The drill string 52 is directed to a position in alignment with the tubular member 24 and the drill string 52 is rotated to the right to cause the mateable threads to come together to -connect the drill string 52 and the tubular member 24. After threaded connection between threads 53 and 38 is fully taken up, the weight of the drill string 52 on the tubular member is maintained neutral and the drill string is continued to be rotated in a right-hand direction. This rotation causes the lefthand threads 36 and 37 in the upper portion of the tubular member 24 and the upper adapter collar 26, respectively, and the left-hand threads 32 and 33 in the lower adapter collar 27 and the lower portion of the tubular member 24, respectively, to be disconnected, thus freeing tubular member 24 from connection with the casing sections 21 and 22. As shown in FIGURE 4 the tubular member 24 is then removable from the well by simply pulling up drill string 52. The threads 33 on the lower end of tubular member 24 are of a small enough diameter to pass through the interior of adapter collar 26. Thus the tubular member 24 is removed from the hole leaving only the protective sheath 40 closing olf the well between the two casing sections 21 and 22. The protective sheath 4t] and the cement 51 are then removed by suitable mechanical or chemical means to expose the producing interval of the well.

The tubular member and the accompanying protective sheath of the present invention provide a means for easily opening a window in the well casing at a selectedinterval in the well. Windows of feet and more can be opened using the method and apparatus of the present invention. The method and apparatus are particularly useful in opening longer windows, for example 500 feet or longer. In some operations, particularly when it is desirable to open the longer windows, it may be desirable to mechanically cut the lower connection between the tubular member 24 and the adapter collar 27. This is because the great length of the tubular member 24 may prevent neutralizing the weight at both the upper and lower connections simultaneously thus causing one of the sets of threads to bind. If this is found to be the case,

the lower end of tubular member 24 is freed by cutting the tubular member at or just above threads 32 with a conventional milling tool or other conventional cutting means. The drill string then is used to disconnect only the upper threaded connection between the casing and the tubular member. The tubular member is then pulled from the hole in the manner heretofore described.

After the tubular member is disconnected from the casing string and removed from the well, only the protective sheath and the hardened cement remain between the well and the producing interval 80. In accordance with the invention the protective sheath 40 is formed from a material which is easily millable and which thus may be removed with the cement by conventional cement removing means. Thus it is a relatively easy matter to cut away both the protective sheath 40 and the cement 51 with an expanding bit on the end of a drill string. Since there is no steel casing left in the interval which is to be opened, the cutting is a simple and economical operation.

It is also in accordance with the invention to dissolve or otherwise wash out the protective sheath by circulating a preselected fluid substance in the well. For example, when paper board pipe is used as the protective sheath, it is removable by circulating hot water or brine in the well to cause the paper board to disintegrate and to be carried out of the well in the circulating water or brine. In a like manner a solvent may be used to remove plastic if desired.

Referring now to FIGURES 6-9, a running-in method useful in positioning a casing string which includes therein the apparatus of the present invention will be more fully described. As shown in FIGURE 6 a well has been drilled into the earth 79. A-casing string 72 is being run into the well. A first casing section 7l has been connected to casing section 72 and the pair of easing sections are being lowered into the well through a drilling platform 74 and turntable 73 by means of a suitable means such as elevators 75 and wire line 76. A casing section or a stand of easing sections is run down into the well while being held at the upper end by the elevators 75. Slips are then placed in turnable 73 against the casing to hold the casing. The elevators 75 are released and they are used to pick up another stand of easing. This stand is connected to the casing string held at the turntable and the slip removed. The elevators 75 are lowered to run the newly connected stand into the well. Thus the casing string is formed and lowered into the well.

In accordance with this invention then, if it were desirable for example to open a window between the 2000 and 2500 levels of a 4000 Well and to case and cement the rest of the well in a conventional manner, a 1500' string of easing would first be run in the well as described above. For ease in describing the invention, assume that casing section 72 as shown in FIGURE 7 represents the upper casing section in the 1500 string of casing and that it is desirable to have the next 500' section removable from the casing string after the entire string has been run into the well and cemented in place. Therefore, a 500-ft. tubular member and protective sheath must be connected into the casing string starting at casing section 72.

The casing string is hung in the well by inserting slips into the turntable 73 about the upper end of easing section 72. A tubular member 77 is connected to the easing section 72 using suitable means such as an adapter collar 27 as heretofore described. A protective sheath 78 is formed in a fluid-tight manner around the lower connection between the tubular member 77 and the easing section 72. A preferred protection sheath 78 is a pipe of greater diameter than the tubular member and approaching the diameter of the casing sections, which pipe is formed of an easily removable or more easily drillable material compared to steel such as plastic, rubber, paper,

cement, or an easily drillable metal. Thus the protective sheath is formed with a material having a relatively low mechanical strength. The protective sheath is sized to fit loosely around the tubular member and to be originally slidable thereon. Therefore the protective sheath can be slid up out of the way if necessary while the connection between adapter collar 27 and casing section 72 is being made. After this connection is made the protective sheath is securely fastened around adapter collar 27 to prevent fluid from contacting the tubular memher.

The upper end of the protective sheath 78 is provided with a telescoping portion 81 which is telescopically slidable over the main portion of the protective sheath 78. The telescoping portion 81 is initially retracted as shown in FIGURE 7 to expose the upper portion of the tubular member 77 so that running-in operations which require that the steel tubular member be securely held by both power tongs and slips 90 and 91 may be accomplished without damaging the relatively weak protective sheath. Thus the lower connection between the tubular member and the casing section or another tubular section is made, the protective sheath is secured at this connection, the tongs and slips are used freely on the exposed upper portion of the tubular member to lower the entire string into the well and then to hang the entire string while a new stand is connected. The telescoping portion 81 has a collar 85 which fits securely around the adapter collar 26.

Referring to FIGURE 7 and FIGURE 8, it is seen j that slips 0 and 91 are used in the turnable 73 against tubular member 77 to hand the casing string in the well. If tubular member 77 is the last tubular member to be connected into the string for example and it is desired to continue with more casing sections, a casing section or a stand of casing sections 83 which might be two or three casing sections connected together would be screwed up by suitable means such as power tongs and a suitable connection made between the casing section 83 and the exposed upper portion of tubularmember 77. A suitable connection is made, for example, using adapter collar 26 in the manner heretofore described. The slips and 91 are removed and the entire casing string is supported by elevators 75 secured to casing section 83.

The telescopic portion 81 of the protective sheath 78 is then extended to cover the tubular member as shown in FIGURE 9. The telescopic portion is secured in place and the portective sheath prevents cement from contacting the tubular member. If so desired, a lubricating fluid can be placed between the protective sheath and the tubular member to facilitate later removal of the tubular member.

A lubricating or pressure equalizing fluid can be posi tioned in the annular space between the tubular member and the protective sheath. This liquid may be for example drilling mud. The lubricating fluid is desirably added as each section of the tublar member and protective sheath are run into the hole. The lubricating fluid prevents the cement from crushing the protective sheath and thus sticking the tubular member in the borehole.

Although only a few embodiments of the invention have been specifically described, the inventive concept is not limited by these embodiments but is meant to include all equivalents embraced by the scope of the claims.

We claim:

1. Apparatus for connecting at least a pair of spacedapart casing sections for cementing in a well comprising a tubular member, said tubular member having a smaller outside diameter than the inside diameter of any casing sections to be positioned in the well above said tubular member, first means on one end of said tubular member connectable with one of said casing sections, second means on the other end of said tubular member connectable with the other of said casing sections, a protective sheath formed around said tubular member and forming an annular space with said tubular member, means connecting said sheath to one of said casing sections and forming a fluid-tight seal between one end of said protective sheath and said one of said casing sections, means connecting the other end of said sheath to the other of said casing sections and forming a fluid-tight seal between the other end of said protective sheath and the said other of said casing sections to form a closed annular space between said sheath and said tubular member and a lubricating fluid in said annular space between said tubular member and said portective sheath.

2. The apparatus of claim 1 further characterized in that the upper end of said protective sheath includes a portion which is telescopically slidable over the main portion of said protective sheath to selectively expose the upper portion of said tubular member.

3. A method of completing a well for production from a long interval comprising the steps of forming a casing string including at least a portion thereof of smaller outside diameter than the inside diameter of the remainder of the casing string located above said portion, forming a protective sheath around said portion, to provide an annular chamber between said portion and said protective sheath, at least partially filling said angular chamber with liquid, sealing said protective sheath to the casing string above and below said portion to form a closed annular chamber between said portion and said sheath positioning said casing string in a well, flowing cement into the annular space between said casing string and said well, allowing said cement to set, and removing said portion of said casing string from said well.

4. The method of claim 3 further characterized by the step of removing said protective sheath from said well.

5. The method of claim 4 where the protective sheath is mechanically removed.

'6. The method of claim 4 where the protective sheath vis removed by circulating a fluid in said well to reduce the competency of said sheath and to flow said sheath out of said well.

7. Apparatus for connecting a pair of spaced-apart casing sections for cementing in a well comprising an elongated tubular member having a smaller outside diameter than the inside diameter of easing sections connected above said tubular member in said well, said tubular member being long enough to bridge a seiected produc ing interval, a pair of adapter collars, one of said adapter collars connected to the end of the casing section above said tubular member and the other of said adapter collars connected to the end of the casing section below said tubular member, first thread means on the outsideupper end of said tubular member releasably connectable with the adapter collar of the casing section above said tubular member, said thread means on the lower end of said tubular member releasably connectable with the adapter collar of the casing section below said tubular member, said first and second thread means having threads 'cut in the same direction, engageable means in the upper portion of said tubular member for engagement by a well tool for rotating said tubular member in a direction to disengage said first and second thread means from the casing sections and to remove said tubular member from the well, protective sheath means around said tubular member and forming an annular chamber with said tubular member, said tubular member being rotatable within said protective sheath means and removable therefrom and means connecting said protective sheath means to the casing section immediately above and below said tubular member to form a fluid-tight annular chamber between said sheath means and said tubular member.

8. Apparatus as in claim 7 further characterized by the said engageable means in the upper portion of said tubular member being third thread means on the interior of the upper portion of said tubular member, said third thread means having threads cut in the opposite-direction from said first and second thread means.

9. Apparatus as in claim 7 further characterized in that the protective sheath means is formed of a material selected from the group consisting of plastic, paper and rubber.

10. Apparatus as in claim 8 further characterized by said well tool being a drill string having a threaded end for engaging the third thread means of said tubular member.

11. Apparatus as in claim 9 further characterized by a liquid at least partially filling the annular chamber between the tubular member and the protective sheath means.

References Cited by the Examiner UNITED STATES PATENTS 65,238 5/1867 Laing 285-386 159,805 2/1875 Dobbs 166--21 403,751 5/1889 Hart 166158 1,639,065 8/1927 Thagard 1753 18 1,834,946 12/1931 Halliburton 16621 2,173,033 9/1939 Armentrout et al. 166 46 X 2,215,913 9/1940 Brown 16637.X 2,219,022 10/1940 Salinkov 166-37 X 2,224,565 12/1940 Flude 166-442 X 2,479,394 8/1949 Montgomery 166-37 X 3,128,825 4/1964 Blagg 1662A?.

CHARLES E. OCONNELL, Primary Examiner. 

3. A METHOD OF COMPLETING A WELL FOR PRODUCTING FROM A LONG INTERVAL COMPRISING THE STEPS OF FORMING A CASING STRING INCLUDING AT LEAST A PORTION THEREOF OF SMALLER OUTSIDE DIAMETER THAN THE INSIDE DIAMETER OF THE REMAINDER OF THE CASING STRING LOCATED ABOVE SAID PORTION, FORMING A PROTECTIVE SHEATH AROUND SAID PORTION, TO PROVIDE AN ANNULAR CHAMBER BETWEEN SAID PORTION AND SAID PROTECTIVE SHEATH, AT LEAST PARTIALLY FILLING SAID ANGULAR CHAMBER WITH LIQUID, SEALING SAID PROTECTIVE SHEATH TO THE CASING STRING ABOVE AND BELOW SAID PORTION TO FORM A CLOSED ANNULAR CHAMBER BETWEEN SAID PORTION AND SAID SHEATH POSITIONING SAID CASING STRING IN A WELL, FLOWING CEMENT INTO THE ANNULAR SPACE BETWEEN SAID CASING STRING AND SAID WELL, ALLOWING SAID CEMENT TO SET, AND REMOVING SAID PORTION OF SAID CASING STRING FROM SAID WELL. 